thunderbolt: Switch to use device_property_count_uXX()

Use device_property_count_uXX() directly, that makes code neater.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Yehezkel Bernat <YehezkelShB@gmail.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>